Programmable infusion pumps are used to carry out controlled delivery of liquid food for enteral feeding and medications for various purposes, for example pain management. In a common arrangement, an infusion pump receives a disposable administration set comprising a cassette removably received by the pump and flexible tubing connected to the cassette for providing a fluid delivery path through the pump.
The administration set may include a pumping segment of tubing that wraps around a rotor mechanism of the pump, and the cassette may include a pair of tubing connectors to which opposite ends of the tubing segment are connected. The rotor mechanism may have pinch rollers or fingers that deform the tubing segment as the rotor rotates to progressively urge fluid through the tubing in a peristaltic manner. The cassette may have another pair of tubing connectors for connecting inflow tubing carrying fluid from a fluid source and outflow tubing leading to a patient. As a result, a flow path is provided from the inflow tubing, through the tubing segment, to the outflow tubing.
It is known to provide an in-line occluder as part of the cassette as a safety feature for preventing unintended free-flow of fluid to the patient if the pump is not in an operating mode. The in-line occluder may be incorporated into one of the tubing connectors of the cassette. A flow path passing the occluder may be intentionally established by engaging the flexible tubing at a predetermined location near the in-line occluder. For example, a projection on a door of the pump may be arranged to engage the tubing when the door is closed in order to open a flow path as disclosed in U.S. Pat. No. 7,815,612.
One challenge posed by in-line occluders is that they make it difficult for a person to manually prime the tubing of the administration set in order to remove air from the tubing and fill the tubing with liquid before infusion to a patient. While automated priming may be an option, wherein a user loads the administration set tubing into the pump and operates the pump to advance the fluid, automated priming has recognized drawbacks. For example, the pump may deliver fluid at a slow rate during priming and it can take quite a long time to complete priming. In emergencies, such a time delay may not be desirable. Another problem associated with using the pump for priming is that the attending person may begin to perform other tasks while automated priming continues, and may neglect to adequately monitor the administration set tubing as priming comes to completion. So, it is highly desirable to provide manual priming as an option.
The ENTERALITE® INFINITY® and INFINITY ORANGE® infusion pumps available from Zevex, Inc., the applicant herein, operate with a cassette having an in-line occluder. In order to manually prime the administration set, the user is instructed to gently pinch the tubing between the thumb and index finger at a location corresponding to the in-line occluder to open a flow passage, while also holding the bag of fluid above the cassette and squeezing the bag to force fluid past the occluder. If pinch pressure is too strong, or is applied in the wrong location, there is risk of damaging the in-line occluder and thereby hampering its effectiveness. There is also risk that the user will dig his or her fingernail into the tubing and puncture the tubing, thereby causing a leak.
In order to facilitate manual priming, it is known to provide a cantilevered priming arm on the cassette that extends alongside the tubing and has an actuator pad at the unsupported end of the arm. This type of priming arm is disclosed in U.S. Patent Application Pub. Nos. 2011/0082438 and 2012/0083737. The priming arm may be flexed to manually press the actuator pad against the tubing at a predetermined location to open a fluid passage past the occluder. The priming arm acts as a spring that removes the pad from the tubing when manual pressure is released so that the in-line occluder will once again block flow. This solution adds cost and complexity to the cassette design, and the flexible priming arm may break if the cassette is mishandled.
What is needed is a cassette that enables manual priming of the administration set tubing without the problems noted above.